In a communication network of a communication company, a radio device of a subscriber and a radio device for a self line, a sub-millimeter-wave band or a millimeter-wave band having comparatively high frequencies is frequently used, or optical communication or the like is also used for effective use of a frequency and from characteristics of a broad band system. Especially in the former case, as an antenna for the radio device, there is used a parabola antenna having pencil beam characteristics capable of obtaining a high gain, or a planar antenna in which a plurality of antenna unit elements are arranged in an array form. As a method of aligning an azimuth of such an antenna having the directivity, a method has been used in which an optical aiming unit shown in FIG. 8 is attached in parallel with a main beam of the antenna whose azimuth is to be aligned, and a target such as a counter antenna is aligned with the center of such a graduation line as shown in FIG. 9 with naked eyes.
However, since the optical aiming unit is expensive and is more expensive than an antenna main body sometimes, the unit cannot be attached as a standard, and is used as a tool for an antenna installation work in many cases. Especially in a sub-millimeter-wave, millimeter-wave or optical communication in which it is technically difficult to obtain a large transmission power, a pencil beam antenna having a large gain is indispensable, and it is a large theme to economically provide means for aligning the azimuth of this antenna for promotion of use of the frequency band.
Moreover, as means for solving the above-mentioned problem, a station antenna of a subscriber is proposed in which a central axis of a viewing hole formed at a peripheral portion of an antenna portion and a central axis of a viewing hole formed at an attachment fitting for attaching the antenna portion and a radio portion to a column have the same direction as that of the directivity of the antenna portion, and these central axes are arranged along the same line.
However, there has been a problem that when a sufficient distance is not disposed between an opening on a target side and an opening on an operator's viewing side, precision cannot be achieved.
An example of FIG. 6 will be described.
When a distance H between an opening 6B on a target side and an opening 6C on an operator's viewing side is small, deviation is generated in accordance with a viewing position of a visual position 6A, that is, a distance A. FIG. 7 shows that the operator looks through an aiming hole structure at this time. That is, in this example, a distance h in FIG. 7 seems to be large, but the distance H decreases or the distance A increases, depending on a ratio between the distance H as a thickness of the aiming hole structure and the distance A from the opening 6B on the target side to the visual position 6A viewed from the opening. In consequence, the opening 6B on the target side is superimposed on the opening 6C on the operator's viewing side, and distinction cannot be made. In this case, it cannot be judged whether or not a visual point or position deviates, and therefore the antenna cannot be installed in an appropriate direction.
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-72557